A variety of implantable medical devices (IMDs) are available to monitor physiological conditions within a patient, deliver therapy to a patient, or both. Typically, an IMD is coupled to one or more implantable leads that carry electrodes to sense physiological electrical activity or deliver electrical stimulation. Cardiac pacemakers and cardioverter-defibrillators, for example, are coupled to one or more intravenous or epicardial leads that include sensing electrodes to sense cardiac electrical activity, stimulation electrodes to deliver pacing, cardioversion or defibrillation pulses, or a combination of sensing and stimulation electrodes.
Neurostimulation systems also include implantable leads for delivery of neurostimulation therapy to patients to treat a variety of symptoms or conditions such as chronic pain, tremor, Parkinson's disease, multiple sclerosis, spinal cord injury, cerebral palsy, amyotrophic lateral sclerosis, dystonia, torticollis, epilepsy, urinary incontinence, fecal incontinence, sexual dysfunction, obesity, or gastroparesis or other gastric mobility disorders. An implantable neurostimulator delivers electrical stimulation pulses via electrodes carried by leads implanted proximate to the spinal cord, pelvic nerves, stomach, or gastrointestinal tract, or within the cranium of a patient, e.g., for deep brain stimulation or occipital nerve stimulation.
As a patient implanted with an IMD moves, some regions of the body may expand and contract, resulting in changes in length. The movement may exert high loading forces on anchors, leads, lead extensions, or body tissue. These forces may cause lead failure, axial migration of electrodes, anchor damage, or tissue damage. The patient may experience pain or operational failure or performance degradation of the IMD.